The present invention relates to surface cleaning systems, particularly cleaning systems suited for cleaning reflective glass panels that are components of heliostats used in concentrated solar energy plants.
The efficiency of concentrated solar field power production depends in part on the ability of the reflective glass panels to reflect and concentrate radiation from the sun onto a heat exchanger positioned on a tower. One factor that can prevent efficient energy generation is low reflectivity caused by dirt, dust, mud and other debris on the reflective panels.
The structures that support and rotate reflective glass panels about two axes of rotation are referred to as heliostats. A typical heliostat structure includes a vertical tubular support for supporting a glass panel support structure. The vertical support has a central vertical axis extending through the center of the tube from end to end and a first drive mechanism that causes the glass panel support structure to rotate about the vertical axis. The heliostat also includes a glass panel support structure with a horizontal rotational axis and a second drive mechanism that causes the glass panel support structure to rotate about the horizontal axis. By providing two axes of rotation, the position of the reflective surface of the heliostat can be altered. The glass panel support structure can rotate about its horizontal and vertical rotational axes at the same time, or at different points in time.
During power plant operation, the power plant control system causes the glass panel support structure to rotate about one or both axes which creates the ability to direct and maintain the reflected sunlight to a specific area on the collector atop of the tower. The control system is capable of moving the glass panels into a substantially vertical resting position when the plant is not in operation, and into a substantially horizontal position during high winds and other conditions. During operation of the power plant, the glass panels may be stationary during periods of time, may move continually or may move intermittently
Reflective surface cleaning systems have been developed that require their own control systems, motorized mechanisms, and in some cases, water and chemicals to clean the reflective surfaces. For example, U.S. Patent Publication 20130306106 describes a motorized dry cleaning system for cleaning rows of photovoltaic solar panels. The cleaning system has a motorized carriage that moves from an upper to a lower edge of a solar panel whose surface is positioned at an angle with respect to the horizontal. The carriage also moves horizontally from panel to panel.
Known cleaning systems require the use of motorized components, independent control systems and power sources to enable the systems to operate. Such systems are costly to build, require a power supply, and the operation of the systems must be integrated into the control system of the concentrated solar power plant. The cleaning cycles must also be coordinated to avoid interfering with power plant operation. It would be desirable to provide a mechanized parasitic system that cleans reflective panels during the normal operation of a solar field, does not require water, chemicals, a power source for operation or an independent cleaning control system to operate and be a fail-safe. In other words, a cleaning system failure would not cause heliostat damage or hinder heliostat operation. It would also be desirable to provide a system that cleans by taking advantage of the normal movements of the heliostat during operation such that no additional manipulation or movement of the heliostat is needed to accomplish cleaning.
For these and other reasons, a need exists for the present invention.